Heating greenhouse with house boiler's exhaust
The exhaust pipe from our 96%-efficiency heater/boiler (single unit) comes out from the wall low (about 4 feet from the ground) and it annoys me to see, how warm the exhaust is - I'm heating the sky...
Can I build a small greenhouse next to that wall - and have the pipe open into it?
I already asked on the gardening forum, whether the plants will like it. I'm asking here, whether the boiler will object in any way. Also, if someone could spell-out, what gases exactly are to be found in the exhaust... I know, the mixture is not good for breathing, but would anything be damaging to the veggies (or to the people, who'll later eat them)?